上游弯管对超声波流量计精度影响及整流设计

针对上游弯管流场变化对超声波流量计测量精度的影响,利用CFD对测量管道内部流场进行数值仿真模拟,并设计整流器改善由弯管导致的明显的二次流和涡流等情况,以减小超声波流量计测量误差。研究对象为基于时差法的DN15超声波液体流量计,流量范围在0.1～1.5 m~3/h内,上游弯管与流量计之间测试直管段距离为2～20D。对比超声波流量计加装整流器前后测量误差,通过实验结果验证,未整流时流量计随着直管段越短测量误差越大,安装的整流器可以改善管道内流场的速度分布,将直管段长度缩短为10D,提升超声波流量计测量误差满足在±1.5%以内,验证了数值模拟的正确性,对工程实际应用具有一定指导意义。     

斜插式超声流量计探头插入深度影响实验研究

研究了DN500和DN1000口径斜插式超声流量计探头安装位置影响误差,针对凸出、相切和凹陷3种探头安装位置分别进行了实验研究.得到了不同探头安装位置对流量计流量测量引入的误差,分析了探头影响误差的来源,深入剖析了流量计表体大小及声道数与探头安装位置引入误差的关系.通过分析给出按照相切位置安装探头的流量计不需进行探头位置影响误差修正,按照凸出位置安装的流量计可以使用修正公式进行修正,修正后流量误差接近于零.凹陷探头修正声道范围影响误差后,流量测量误差变为正值,其探头流场扰动影响需要积累较多数据后根据经验进行修正.     

超声波流量计整流器优化设计

气体超声波流量计的测量精度由飞行时间的测量精度和流量计自身的流场适应性决定,流量计的流场适应性又由流量计的声道布置和整流器的性能决定。文章设计了一种内嵌于流量计的整流器,详细阐述了该整流器的结构、各模块的功能。介绍了整流器性能优化的理论依据、过程以及整流器性能优劣的判别准则。该整流器性能优化主要取决于起旋器的优化,文章给出了装有8片起旋器和装有10片起旋器的整流器在直管、单弯管下的性能参数对比,试验结果显示装有10片起旋器的整流器有着更好的流场适应性：重复性满足国标要求,直管示值误差与弯管示值误差的差值<0.3%。文章的创新点在于给出气体超声波流量计整流器设计和优化的理论依据和一整套流程,对于设计气体超声波流量计整流器的科研人员有借鉴意义。     

大口径超声波流量计高精度低功耗方案设计

针对影响超声波流量计测量精度和功耗的关键环节——超声波时差测量,设计了以超低功耗处理器EFM32G880F128为控制核心,以高精度、低功耗的超声波模拟前端芯片TDC1000和数字转换芯片TDC7200构成时差测量电路的控制系统,较好地控制了在回波信号的放大及接收过程中产生的误差及功耗,有效地提高了电池供电、大口径超声波流量计的测量精度,降低了产品功耗。经过检验,其测量误差低于1%,能够满足市场需求,具有良好的应用前景。     

大管径超声波测流误差的影响因素及修正分析

流量测量是影响水轮机效率测试精度最主要的因素。大管径流量测量的方法主要采用超声波法,然而,其测量精度及误差构成尚无有效的校验方法。结合时差法超声波流量计的测流原理,推导得到流量综合误差,建立测流误差描述模型。提出一种基于流量测量理想系统来进行误差分析的量化方法,为超声波测流系统的误差分析与控制提供一种新的途径。通过测流理想系统对超声波测流精度的影响因素进行仿真研究,分析了各项参数测量误差对系统综合误差的影响,针对影响较大的主导因素提出了相关修正方法,并对系统综合误差的控制进行了分析。最后搭建实验系统进行研究,实验结果初步验证了该方法的有效性。     

基于双MCU的高精度低成本超声流量计

针对传统超声流量计精度低、功率损耗大的问题,研制了一种新型超声波流量计.该流量计采用高速CMOS计数器74AC161,选用133 MHz高精度,高稳定度频率振荡器,提高测量精度同时降低成本.采用环鸣法,设计阈值电路、过零电路,减小测量误差,提高测量精度、增强了抗干扰能力.实验结果表明:该超声流量计在计时方面具有高的准确度和可靠性,保证了流量测量精度,简化了电路设计,降低了设计成本,达到了预期设计要求.     

超声波气体流量计检测精度影响因素分析

在天然气的管道运输过程中,提高气体流量测量的精度是提高运输效率、避免安全事故发生的关键技术。利用流体力学仿真（CFD）方法建立组合双弯管及变径管道模型,定量计算修正系数,对双声道超声波流量计结构和安装位置对于管道内气体速度场的影响进行研究。通过仿真得出超声波流量计的最优声道位置,并结合实验验证了仿真结果的可信性。模拟结果表明,双弯管和变径管与超声波流量计的安装位置至少为10D才能保证流体充分流动;通过修正系数随雷诺数的变化情况得出双声道超声波流量计的最优声道位置为距管道截面中心0.25D处。研究结论对于不同性质气体的流量检测同样适用,为工业中气体运输检测精度的提高以及超声波流量计的优化提供了依据。     

基于立体视觉的旋翼共锥度动态测量系统精度分析

为了提高基于立体视觉的直升机旋翼共锥度动态测量系统的精度和可操作性,全面分析了其测量误差。首先,介绍了测量系统模型及误差来源;其次,分析了双目立体视觉静态三维测量的误差;再次,针对旋翼共锥度的多目标动态测量特点,分析了系统安装误差对共锥度解算精度的影响;最后,利用原理样机进行了6 058次静态测量重复实验,通过统计分析可知静态测量误差小于1.4 mm。对动态测量误差进行了仿真实验分析,给出了各参数对精度影响的量化结果,为实际共锥度测量的误差控制提供了理论依据。在标记点安装精度小于10 mm的情况下,动态测量误差小于3.5 mm,合成产生的总测量误差小于4.9 mm,能满足旋翼共锥度动态测量精度要求。     

单弯管下游超声流量计的安装和测量性能研究

对大管径多声道超声流量计在单弯管下游流场中的安装和测量性能进行了数值仿真研究,分析了超声流量计在0.1 m、1 m和10 m口径下不同流速、声道数、旋转角以及前直管段长度时测量误差的变化规律。仿真结果表明,交叉声道布置形式对弯管产生的二次流所引入的横向测量误差有很好地抑制作用;对于大口径弯管下游流量测量,采用交叉4声道且将超声流量计安装在弯管下游5D位置可以获得1%的精度,且随着声道数的增多测量误差有减小的趋势;相同雷诺数时的测量误差基本相同。研究结果可为大管径多声道超声流量计的实际安装和使用提供一定的参考。     

电动舵机减速器扭矩测量误差分析与补偿

减速器的扭矩输入输出特性是衡量电动舵机性能的重要指标.在测量实验中,由于机械安装,轴承摩擦和电机驱动器非线性等原因造成的误差会折算到扭矩测量结果中,导致扭矩测量误差并降低精度.以减速器为研究对象,通过动态方程建立电动舵机系统的数学模型,提出将扭矩测量误差进行分离,令机械安装与轴承摩擦作为已知的系统误差,最终得到电机驱动器误差的观点,采用基于最小二乘的曲线拟合算法,对实测静态和动态数据进行预处理从而对扭矩测量误差进行补偿.实验结果说明此方法能够补偿电机驱动器非线性引入的测量误差从而提高测量精度.     

Particle image velocimetry flowmeter for natural gas applications

Ultrasonic flowmeters are currently used in the measurement of large natural gas flow. However, their high sensitivity to noise signals can cause measurement errors and direct economic losses. Particle image velocimetry (PIV) measurement technology has several advantages, including convenient installation and maintenance, and strong anti-interference ability, thereby presenting an innovative idea for its application in the field of flow measurement. In this paper, a cyclic integration method is proposed for the application of PIV technology in flow measurement of natural gas. The results show that PIV flowmeter and ultrasonic flowmeter are basically consistent, and the maximum deviation is about 2%. confirming the feasibility of the PIV flowmeter. Therefore, this study provides a theoretical and technical reference for the development of a PIV flowmeter for natural gas.     

The development of a multiphase flow meter without separation based on sloped open channel dynamics

The online continuous measurement of multiphase flow is one of the most key technologies which influences the development of oil industry in future. A new type of multiphase meter system is developed based on the open channel flow. The test pipe of the meter is slightly slopped to make the flow pattern mainly stratified flow. Based on the study of oil and gas flow dynamics in the open channel test pipe, the liquid metering model and gas metering model are deduced to calculate the gas and the liquid flow rate, the water cut is measured online by the principle of differential pressure. This device can work online without the separation of the production fluid. By the lab test and field application test, the results of the metering system show that the liquid flow rate errors are within ±5%, the gas flow rate errors can be within ±5%, and the water cut absolute error is within ±2%, which can meet the demands of the field flow rate measurement.     

Systematic investigation of pipe flows and installation effects using laser Doppler anemometry—Part II. The effect of disturbed flow profiles on turbine gas meters—a describing empirical model

For systematic investigations of installation effects and for finding efficient ways to minimise these effects, a research project was initiated at the PTB. It covers the design of an automated test facility using a laser Doppler anemometer, the measurement of velocity profiles downstream of several pipe configurations and flow conditioners, as well as the measurement of the change in the gas meter behaviour, namely the shift of the error curve due to the disturbed velocity profiles.

Part I of this paper (presented in this issue) describes the test facility for the investigation of installation effects and shows the relation between pipe configuration and disturbed flow profile for a wide variety of pipe configurations and flow conditioners.

The second part compares the error shift of turbine meters with the characteristic of disturbed flow profiles. For this, three flow field parameters are used to quantify the disturbances of the velocity profiles such as the swirl intensity, flatness and asymmetry of the profile. Considering this, an empirical model is presented to explain the error shift of a turbine meter as a function of these three flow field parameters. The model will be verified for three types of turbine meters and the results will be discussed.     

TDC-GP21在超声波热量表中的应用

介绍了基于增强型高精度时间数字转换芯片TDC-GP21的超声波热量表的具体设计方案。流量测量采用超声波时差法原理,利用MSP430F4152单片机控制TDC-GP21进行超声波传播时间和流体温度差的测量,提高了系统的测量精度,大幅降低了系统的功耗和成本。通过流量标定,系统测量结果可达热量表行业标准2级表要求。     

The manufacturing of ultrasonic gas flow meters

From their introduction, ultrasonic flow meters have received a rapid acceptance as being one of the favored measurement methods for high accuracy custody transfer applications in high-pressure gas transmission systems. There are many benefits when using ultrasonic technology; increased rangeability and capacity over conventional measurement technology with unparalleled accuracy are near the top of the list. But in many cases, even more important are the cost savings obtained due to the decrease in maintenance costs and savings in compressor fuel cost by the reduction of the pressure drop through the station. Key elements in the success of the ultrasonic technology are the manufacturing methods and procedures that result in tight tolerances in the geometry of the meter. Whereas the accuracy of the meter is mainly dependent on the quality of the geometry and accuracy of the time measurement, the stated performance of the meter can be guaranteed based on a dry calibration only; a practice identical to the widely accepted orifice measurement. The purpose of this paper is to focus on the influence of the manufacturing tolerances on the uncertainty of the measurement, the dry calibration procedure and the final comparison with the results obtained after wet calibrations.     

基于物联网的高精度超声波气体流量监测系统设计

针对工业现场超声波流量计要求较高精度,简化现场布线,对安装现场进行监控预警又要远距离传输数据的需求,设计了一种基于物联网MQTT协议和ESP8266芯片的高精度超声波气体监控系统。使用DHT22测量温湿度、MQ-4测量甲烷浓度。为提高超声波流量计的精度,使用Z式探头安装法与MAX35104高精度气体测量芯片。采用STM32F103ZET6作为主控MCU,实现对外围电路的控制及数据处理。为实现远程控制与无线传输数据,采用ESP8266芯片通过网络传输数据。实验证明,该系统实现了测量现场的布线简化、危险环境监控和远程数据传输,可以进行气体流量测量,成本较低,可靠性高。     

超声波技术在核电厂给水流量测量中的应用

为了解决差压式流量计在主给水流量测量中存在的问题,将超声波技术应用到主给水流量测量中。开展了主给水流量精度对于核电厂反应堆热功率计算及其不确定度影响的分析,总结了国内外核电厂通过提高主给水流量测量精度的方式进行核电厂小幅度功率提升的研究成果和实践经验。分析了国内在建的AP1000核电厂中,通过采用超声波流量计进行主给水流量测量以及进行小幅度功率提升项目的意义、可行性、需要开展的工作以及实施该项目潜在的收益和风险。研究结果表明,基于超声波技术完成主给水流量测量,可以实现AP1000核电厂的小幅度功率提升,同时可以使核电厂更加安全、稳定和有效地运行。     

Influence of flow disturbances on the performance of industry-standard LNG flow meters

In the last decade significant progress has been achieved in the development of measurement traceability for LNG inline metering technologies such as Coriolis and ultrasonic flow meters. In 2019, the world's first LNG research and calibration facility has been realised thus enabling calibration and performance testing of small and mid-scale LNG flow meters under realistic cryogenic conditions at a maximum flow rate of 200 m³/h and provisional mass flow measurement uncertainty of 0.30% (k = 2) using liquid nitrogen as the calibration fluid. This facility enabled, for the first time, an extensive test programme of LNG flow meters under cryogenic conditions to be carried out to achieve three main objectives; the first is to reduce the onsite flow measurement uncertainty for small and mid-scale LNG applications to meet a target measurement uncertainty of 0.50% (k = 2), the second is to systematically assess the impact of upstream flow disturbances and meter insulation on meter performance and the third is to assess transferability of meter calibrations with water at ambient conditions to cryogenic conditions. SI-traceable flow calibration results from testing six LNG flow meters (four Coriolis and two ultrasonic, see acknowledgment section) with water in a water calibration facility and liquid nitrogen (LIN) in the LNG research and calibration facility under various test conditions are fully described in this paper. Water and LIN calibration data were compared and it was observed that the influence of removing the meter insulation on mass flow rate measurement accuracy can be more significant (meter error > ±0.50%) than the influence of many typical upstream disturbances when the meter is preceded by a straight piping length equal to twenty pipe diameters (20D) with no additional flow conditioning devices, in particular for ultrasonic meters. The results indicate that the correction models used to transfer the water calibration to cryogenic conditions (using LIN) can potentially result in mass flow rate measurement errors below ±0.5%, however, the correction models are specific to the meter type and manufacturer. This work shows that the target measurement uncertainty of 0.50% can be achieved if the expanded standard error of the mean value measured by the meter is smaller than 0.40% (k = 2). It is planned to repeat these tests with LNG in order to compare the results with the LIN tests presented in this paper. This may reveal that testing with an explosion safe and environmentally friendly fluid such as LIN produces representative results for testing LNG flow meters.     

Field test of a swirlmeter for gas flow measurement

In this paper the experimental results of a field test in natural gas measurement are presented. A vortex precession meter (swirlmeter) has been tested by means of a master–slave calibration technique, using, as reference, a turbine gas meter for custody transfer. The main aim of this study is to assess the metrological behaviour and the sensibility to the installation effects of a vortex precession flowmeter (swirlmeter), which, although well known in the control of the process industry, is quite a new instrument in natural gas applications. The experimental results here reported can be considered as only a first but necessary step to realise an exhaustive metrological analysis of this meter, since field tests must always be combined with laboratory tests in order to reach a comprehensive knowledge.